Phase Relationship Calculations

Understanding the phase relationships of soil (solid, water, air) is fundamental to geotechnical engineering and material properties.

Example

A soil sample has a total wet mass of 20 kg and a total volume of 0.01 m3m^3. After being dried in an oven, the dry mass is 16 kg. The specific gravity of the soil solids (GsG_s) is 2.65. Calculate the moisture content (ww), bulk density (ρbulk\rho_{bulk}), dry density (ρdry\rho_{dry}), void ratio (ee), and degree of saturation (SS). Assume the density of water (ρw\rho_w) is 1000kg / m31000 \text{kg / m}^3.

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Thermal Expansion of Materials

Different materials expand at vastly different rates when heated. This differential expansion can cause catastrophic stresses if materials are rigidly bonded together (e.g., an aluminum frame holding a glass pane, or steel embedded in concrete).

Example

A perfectly rigid aluminum window frame holds a pane of annealed glass. The original length of the glass pane is exactly L0=2.000L_0 = 2.000 m at 20C20^\circ \text{C}. The coefficient of thermal expansion for aluminum is αAl=23×106/C\alpha_{Al} = 23 \times 10^{-6} /^\circ\text{C} and for glass is αglass=9×106/C\alpha_{glass} = 9 \times 10^{-6} /^\circ\text{C}. If the temperature rises to 50C50^\circ \text{C} and the glass is rigidly restrained by the much stiffer aluminum frame (which forces the glass to expand by the same amount as the aluminum), what is the resulting thermal stress in the glass? Assume the elastic modulus of glass is Eglass=70E_{glass} = 70 GPa.

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Mechanical Properties: Stress and Strain

Understanding the basic relationship between applied force and the resulting deformation is key to material selection and structural design.

Example

A standard structural steel tension test specimen has an original diameter of 12.5mm12.5 \text{mm} and a gauge length of 50.0mm50.0 \text{mm}. A tensile force of 40kN40 \text{kN} is applied, and within the elastic range, the gauge length increases by 0.081mm0.081 \text{mm}. Calculate the applied stress, the resulting strain, and the Modulus of Elasticity (EE) of the steel.

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